Hands down, and legs up, Thailand is a MUST DO.  Pattaya is fine but there is fun to be had in Bangkok and Phuket.  

Never been to either to play but friends have raved about Montreal. The girls are amazing looking and the prices by American standards are quire reasonable. I say London not so much due to English women but bc it is so diverse with beautiful women around the world that travel and live there.

I had a great time in Japan. Now especially with the strong dollar you should have a great time. I stayed with a couple independents rather than going through a service. UK was pretty good also. The rates outside of the US are so much better.

Especially the Cocal in Jaco. It used to be better but now that the Del Rey in San Jose is no longer a huge bordello there's only the Sportsmen's Club there.
In Panama, try the Club Habanero.
I've been to Colombia but only to Cartagena and a friend who's spent a lot of time there says the best city is Medellin.

The spiked drink and kidnap scams are rampant. There are indeed some beautiful women available for P4P fun, but the best-looking women, and best service providers will only be at the top of the price range - perhaps $300-$600+, while the $10-$40 girls are fat, located in really bad neighborhoods, and have drug-dealing pimps.  Plus, how is your Portuguese? Yeah, something to think about...

 
I spent a month in the Philippines this year. A wonderful destination for P4P times if you like petite, submissive Asians at sub-$200 prices. Just beware the Ladyboys (same in Thailand).  Germany has FKK's full of eastern European hotties (around $100-$250-ish). Japan has Soapy Massage and more, but you will need to find places that allow non-Japanese locals to enter.  I've not been to South Korea, but I understand the market is tame by comparison to Thailand and the Philippines.  

 
I suggest you also take a starter trip first - no more than 30 days or so, in maybe 2 places.  Call it a training run where you can ensure you have your travel kit worked out, and get experience dealing with hotels, airfare, transportation, and banking/payments in a foreign country.  Then come home for a few weeks and be better equipped to plan that 5 to 11-month trip.  

 
Life is good

 
The Cat

I've only done P4P overseas a couple of times. My observations:

Some very pretty and fun girls in Melbourne and Sydney Australia.  
Ditto in Lisbon.  
The Pattaya district in Bangkok was grimy, seedy and overcome by dissipation and joyless flesh-peddling. I didn't want to touch anything or anyone there during my fortunately very short visit.

If you get to Prague, please let us know how it goes.

I will add Domincan Republic, especially if you like Latina ladies. They are super reasonably priced and have some that are hot af. You can go to clubs where 1-2 dozen of them will come out and flirt with you hoping to get picked.

My brother loves Thailand!

He travels often & says hands down this is the best bang for your buck. Massages on the beach with top rated service at the fraction of the price. I have never been, but it’s on my bucket list. Congratulations on your retirement!

Amsterdam, where prostitution is legal when business is conducted in four ways which are easily researchable before you go . . . . . .  (Prices can vary dramatically depending on age and looks, just like here.)

 
1.   Window prostitution
2.   Private clubs
3.   Private houses’ (sex clubs without a bar)
4.   Escort agencies

 
Next, if you like Asian women but want to hobby in a safer country, try London.  Their main import is Thai girls (which are more liberal with anal than other Asians).  There are also a good number Japanese and Chinese, almost all of which work through agencies at various incalls scattered throughout the city.  Prices for an hour average about $200-300.

 
Seoul, Korea's best bet is the Gangnam district where many of the Salons are located where female hostesses party with the customers while getting a commission on the liquor consumed.  They will flirt and pick a man to proposition for a sex date at your hotel after their shift is over.  The girl you contract with will overnight with you for $500-600 on average for nice-looking girls, but the top-tier girls, beauty-wise, can run up to $1000.  It's a difficult scene to navigate if you do not have someone with you that speaks Korean.  If alone, you will overpay for EVERYTHING.  

 
The first time I went to Seoul was on a business trip when I learned the importance of not being along when a colleague showed a group of us around several salons.  The second time, I was invited to visit a retired Kgirl I knew from LA and the two of us went together.  She had also been a salon girl before she came to LA to work as a Kgirl, so she knew everything about how salons work over the tourists.  Lol   On two different nights, she helped me pick out a DDG salon girl to take home to her apartment where I was staying for a three-way.   I've done this with her three more times after this.  

 
I haven't tried a sex tour packager, but I know they have them, where you will be escorted by someone who will help you navigate these places.  Just know that you are paying them a fee for their services AND they are also getting a kickback from the clubs for bringing you in, but you won't OVERPAY quite as much as you would on your own.   Even with these experiences, I would still be reluctant to go into these places alone, not speaking Korean, but if you can get a Korean-speaker to show you around, this experience is not to be missed when traveling to Seoul.

Singapore has plenty of legal brothels. I partaked a dozen or so times in my visits there 5-10 years ago. Was really cheap, like USD 40 for 45 minutes ( non-GFE one pop )..  

However, was not really a fan of the whole experience. I much prefer the US GFE+ experience.  I do my homework and try not to pay that much...

Don’t forget Budapest! It’s legal, and the girls are young and hot! I found a combo of massage girls with upsells and escorts - mostly at reasonable prices of $200-$500. Did I overpay? Probably. Was it worth it? Yes!!

You didn't list your tastes: Long time, Short Time, Companion time,  Trophy fucks, GFE, - Asians, Latinas, Euro Girls, Africans, Cheap Charlie/Funds dont matter, Foreign Language Factor or not, Only Mongering/other attractions needed. I can go on.

If you are not American or have a dual passport - Cuba should be on your list

If you drink too much Dont do Colombia or Brazil you will get jacked - If you are not a lush then you will be fine its not scary at all.. I was in So America for 2 months (BA, SP, Cali, La Paz, tiago, Carac). I can communicate in 4 languages (eng, Span, Port, Thai) so it was no difficult to get along.  

if you want plug and Play in Asia - Easiest is PI & LoS.  But there is fun to be have in Indo, Viet, Cambo... along with awesome travels. (if you decide on Asia its easy to jump around with a base most are 1-5 hour flights away) - I am more of a Bangkok Guy than Patts, there are more options in my opinion.  

I cant say much on Europe except FKK's in Germany (eh.. not that exciting for me, Spain easy on streets/clubs pickups in Madrid, Zagreb hot girls but sometimes hard to navigate, Amsterdam was not for me too much transaction but did see a sex show that was interesting.  

 
Last is Ghana - I was in Ashaman once, there is play all over but there is a bit of danger, if you want to see something wild do 1 week its enough.. but different..

So it depends what are your delights.