The number 1 bait on any Gulf of Thailand fishing boat targetting pelagics is the pla thuu. This is a small member of the mackerel family commonly known as Indian mackerel or Longjawed mackerel(Rastrelliger sp.). This is a small, very shiny fish with soft oily flesh and no sharp spines or scutes. Like any of the tunas/macks they are energetic livebaits, tearing away from the boat as fast as possible and often are taken within the first few seconds.
Pla kraw, or yellowtail scad(atule mate) comes a close second place. This is a small trevally and much more hardy than a mackerel bait, able to last hours out under a balloon and seem to feel no ill effects from the hooks. The bigger sized models make a great billfish bait, and work particularly well inshore.
Pla lang keow. Sardine(Sardinella Albella).These are a good bait when available. Usually caught well offshore these baitfish tend to fare poorly in the live bait tank. Losing scales seems to cause them to quickly die, and they are poor at socialising with other fish in the bait tank. As with the mackerel bait, rigging with small hooks to minimise the stress is the way to go with these guys. On a slow day sending out a live sardine will often get results.
Pla goonging. A member of the scad family easily available offshore. Good and strong bait. Smaller ones are great bait for dolphinfish, with bigger sized models working well for macks and billfish. Also makes a fair bottom fishing live bait.
All livebait are caught by jigging sabiki rigs. using 20 kilo line on the sabiki there is often some interesting bycatch. Usually small cobia and tuna, as well as king mackerel. I have been spooled a few times by sailfish that also eat the tiny jigged hooks.
Pla dap. Ribbonfish(Trachipteridae). Used as a dead bait rigged with ganged hooks and either under a float at anchor or slow trolled. Deady on big mackerel and often get taken by sailfish and small black marlin.