There are two steps of change from O-dependence to B. (Immigration name “change the reason of stay”) if current immigration location same with new employer location you can do it all in a day.
Step 1: cancel (or cut) Non O by submit a letter from current visa sponsor with the reason of cancellation. (spouse company). You are able cancel visa 21 days before end date. e.g you want visa ending on 30 Dec. you can cancel it since 11 Dec.
Step 2: Apply Non B by providing your employer documents which contract or offer letter, letter to immigration and other general paper. Make you your visa valid at least 15 days or above.
In case of difference location after cancel visa within 5-7 days you should apply Non B at new location
Non O is stand for Non immigrant O which mean any other type such as dependence, guardian, retirement, medical ect. The requirement of extension in country are specific to which reflection the purpose of why you are in Thailand. E.g
- dependence type require a valid visa and work permit plus certificate of relationships of who you are depending to. -Guardian type require bank statement, letter from school and your kids visa
In fact the family members of person having a work permit also fell into Non O spouse or in another word dependence visa category. Anyway visa application doesn’t identify type of Non immigrant. The consular will grant you what they see fit.
However, it will be matter once you need to extended in country which require
Meaning allows you to do many things legally e.g get a job, have a work permit, Buy a car get local driving license, open bank account and able to stay in country as long as you follow the rule.
If you are non B. It probably already expired because of work permit expired in last April. Thanks to COVID no penalty. But you have to cancel previous visa then Extension with letter from the embassy. Once you have work permit book go to change to proper Non b again.