Topline Digital YouTube Channel
Several major Thai music labels have a strong presence on YouTube, but in my opinion Topline-Diamond is putting out a lot of the most interesting luk thung-molam music of the moment. In addition to topping the charts, they seem especially willing to experiment; you can catch influences from chiptune, prog rock, regional folk genres, etc. They upload their latest hits, older items from their back catalog and even concert footage.
Samakhom Chut Dancer Luk Thung
The flashy and elaborate costumes worn by background dancers are a crucial component of the Thai country music concert. This Facebook group is for designers and fans to share pictures of their outstanding attire. Occasionally NSFW.
Phonthep Lakkhatson's YouTube Channel
Another fantastic collection of videos comes from DJ Phonthep Lakkhatson in the employ of PR Sound, a smaller label that's big in the Khmer ethnic minority areas of Eastern Thailand and South Isan. Specializing in a hybrid of Khmer folk style kantruem and Thai country pop sounds, PR Sound has put out local fiddle-driven dance tunes for decades, with spectacular low-budget MVs to match.
Pleng Pak Jai Radio
One of the best internet forums for Thai oldies, Pleng Pak Jai's front page features an excellent streaming radio program, where the forum's top posters take turns as DJs. Listen to some of Thailand's foremost record collectors playing ultra-obscure records from their personal collections.
Uraniumworld YouTube Channel
Chatchawal Kamsawat from Khon Kaen University has shared a series of beautiful and intimate videos featuring some of the most well known molam performing privately at their homes. This is an unbelievable treasure!
Thai Music Inventory
Put together by Australian researcher James Mitchell, this site has the potential to become a great resource on Thai music for international listeners. Musicological discussions, concert photos and an incredible image database of 78rpm record labels.
Phin Prayuk Youtube Search
Local festivals with raucous live bands are happening all the time in Thailand, and idle band members, friends or other attendees with smartphones frequently shoot video of the events. That means there's a ton of amazing semi-professional material out there. Take for example, this search for พิณประยุกต์ (modernised phin), one of the most popular choices for parade music.