well, IBS is certainly a pain in the ass-and other associated regions. the bloating and gurgling is very unpleasant.
When I was really struggling with it, my onco/haemo consultant here (not a deitician) suggested cutting out lactose and gluten. Very successful. But not immediate as gluten lingers in the system for several weeks. But I was much better fairly quickly and pretrty much cured after a year.
If I regress because I get fed up with being faddy, and eat some pizza, then IBS comes back with a vengeance.
Lactose free is easy, as most shops stock lactose free milk-and CM bread in Nong Hoi has tasty lactose free cheese, but a little normal cheese is not a problem for me.
There is a gf facebook group -gluten free chiang mai that makes the transition to gf easier.
Normal beer is a gluten problem, but Beer lao and Cheers Riceberry (both rice based) are fine for me.
I would suggest cutting gluten and lactose for a few months and see if that helps you.
I also used to take a spoonful of psyllium husk in a glass of water daily. the extra fibre helped
Best of luck. The changes above were life changing for me. Everyone's microbiome is different though -not sure if you have read The Gut Doctor-useful website.