A good idea to bring some of your own gear with you and buy a few bits of tackle when you get to Thailand.
Some rental tackle can be pretty ropey at best. Often the reels are cheap and poorly maintained. They have usually been dunked in the water a few times and may never have been cleaned or properly serviced. There are many stories of anglers losing big fish with poor maintained rods and reels.
Most rods used in Thailand are telescopic and most hired tackle are well to heavy to feel any fight from the fish in some cases fish are lost because of no bend in the rod. So it is advisable to bring a light telescopic rod with you for convenience of travel. You could bring two or three piece rods but experience shows that getting these through customs are sometimes difficult.
I would suggest you bring a reel or two with you. For the ponds with smaller fish a reel holding 100-150m of 8-10lb line is fine. For the heavier fighting fish I would suggest 15- 20lb line and reels to match as all the parks have a few bigger fish in them. For the larger catfish you will need a fairly robust reel. A strong carp reel or one of the big Shimano bait runners is ideal.
You will also need method feeders, waggler floats, swivels, hooks lengths and a few metres of braid. Size 10 and 12 hooks work well for smaller fish, size 8-4 or possibly size 2 for the larger fish. These can be brought with you or purchased at any tackle shop.
Also you may need to bring a small tackle box including, scissors, disgorger, forceps, split shots, pliers etc….
Most fishing venues supply some seating for your comfort however if you want to bring a folding up seat then that’s fine but remember to try and keep your luggage down for travelling abroud