Any recommendations for a bank to store gold and other valuables?

I would suggest you buy yourself a good quality safe and hide it in a "suitable" wall or floor and dont tell anyone

Bangkok Bank has Safe Deposit boxes in a variety of sizes at a number of their Branches. Fees range from 600 baht to 3200 baht per annum

Almost every bank offers safe deposit boxes to its customers. They are usually at the head office, and occasionally at other select branches as well.

There is almost always a waiting list. Waiting times can vary from as short as 12 months to as long as 5 years, the longer times generally for the small, low cost boxes.

Ask at any bank where you have an account and they will give you the details for your area.

Tried 3 main branches in central khon Kaen and they were all full.