Here's some info coming from someone who plays golf in USA, China and Canada. Bangkok has the most affordable golf courses, Phuket is on the higher end. In terms of cost, it's a little on the premium side to gold in Thailand.
Cost break down.
Green fees as a tourist range from 1500 to 4k baht depending on the golf course you visiit. I'll share the best site to book golfing in Thailand at the very end. Also golfing in Thailand does require you to have proper golfing attire/dress code. Be sure to ask where you do go.
Mandatory fees but I'm just going to average up, and this is per person (most courses 99.99% won't allow sharing)
1. Club Rentals 1200 baht
2. Golf Cart 800 baht, per golfer, you can't share a cart with your buddy
3. Caddies 400-800 baht
4. Caddie Tip 400+
5. Transportation to/from (give 1 hour transportation time before tee time) 1k baht 1 way
Overall, expect to pay close to 200-300usd to golf in Thailand. Thailand is a mecca for golfers with some of the nicest courses you will ever play on. The caddies don't usually play for you. I'm one of the worst golfers in the world, I obviously play for different reasons. You can play singles, you can book for more people, you can also end up playing with another couple. Some courses are so busy, you are waiting behind a group of 5+ people. Some are nice to let you play through, some are not.
Here's the good stuff you all really want to know.
Golfsavers.com is the best place to reserve a course/discounts
Suwan Golf & Country Club near Bangkok is the cheapest/one of the nicest places to golf at
Panya Indra Golf Club has the most beautiful caddies out of the 8 or so golf courses I have been to. Most caddies can't speak conversational English but they are good with golfing terminology and the design of each hole. Most will love to encourage you to try out their 19-21st hole bonus course after work. This place also has night golf which I like because it makes it easier to take the caddies with you to dinner afterwards.