For someone who is not living in Thailand I'm really curious about this. I'd appreciate it if someone can include how they reached the top, the song/s that made them known in the country, and most popular member. Thank you!

This may be far from current popularity ranking in Thailand, but based on checking stats on social media here are my observation. Sorry in advance if most of these are wrong. I'm speaking as a foreigner:

Top Girl Groups:
1. PiXXie - Rain, Too Cute, Mutelu, Dejayou and more. I see their songs as being general public friendly. All their group songs have combined millions of views on Youtube alone, from their group songs to solo songs.
2. 4EVE - They seem to keep getting bigger even after the TEST ME viral moment. They got big immediately after that song and the fandom slowly continues to rise since then. Wider song catalog and more endorsements too.
3. Pretzelle - I think their song First Love and U R Mine helped them have a steady fanbase. not too big compared to PiXXie's and 4EVE's, but enough to keep them afloat.
4. BNK48 - popular group name, but I feel like they are struggling a bit with popularity because I noticed mostly new members are active and those who are really popular graduated already.

Top Boy Groups:
1 and 2. BUS and DICE - I'm not living in Thailand and I'm not Thai but their streaming numbers, following numbers, and the amount of people who goes to their events, from mall shows to busking performance, are a lot for a new group.
2. Proxie - Similar to Pretzelle, I think their songs Silent Mode and Unnoticed helped them have a steady fanbase. Their solo songs seems to be doing well too, especially Gorn's.
3. ATLAS - They had a solo concert and there's a lot of support. They also have enough catchy songs in their catalog but I'm not sure if the group ever reached a viral moment.
4. Perses - Compared to other BGs, they have less songs. But seems like Bodyguard is doing well and their management knows how to give them quality songs and content.

Bad Mixy’s latest single Unhappy New Year MV released on Dec 1st featuring Thailands hottest actor, Zee Pruk!

Check out the cute video on youtube:

https://youtu.be/IQMYQ_wZtCw?si=qyZEIewBs68IYeHm