I think you are correct. I'm not sure what's going on since the pandemic hit. In July 2019, the last time I departed Thailand we had business class tickets from BKK to AGS. However, we had to purchase tickets to get us from Ubon to BKK. I knew we were overweight, so I bought 2 tickets for each of us. That didn't work. We couldn't carry extra baggage because we had extra tickets. So, we were 70 KG's over and they wanted a ridiculous price of 1000 baht per kilo. The lady in charge told us we could take our excess baggage and ship it freight by Lion Air (if I remember correctly). She even helped us carry of bags to their location and stayed with us until we completed the process. That was the rules, so that was it. I don't remember the freight charge, but is was not expensive at all. Strangely, the next morning I grabbed a taxi from our airport hotel and headed to the address they gave me. That took me to the Thai Air freight terminal and that's where I picked up about 6 bags. On an additional note, we were seated across the aisle from Mum Jokmok.