I bought Okamura chair costs 2.4K way back 5 years ago or more.
now costs much more.

What u need is a chair with adjustable lumbar support and not too hard but not too soft.
Good seat thickness if possible the seat is adjustable (forward or backward).
Adjustable arm support.

Chair height must be both feet touching the floor (knee 90degrees).

Make sure your table and laptop/monitor is at good height too.

last but not least dont sit too long must get up do stretching.

go see chiropractor to adjust bone and physio learn how to strengthen ur back muscle.