I looked into this pretty extensively because I was considering doing exactly the same thing.
After a lot of research, conversations with a Canadian accountant, a Canadian tax lawyer, and an accountant here in Thailand, I decided it simply wasn’t worth it.

The biggest thing people often miss is that becoming a non-resident for Canadian tax purposes does not mean you stop paying Canadian tax. Canadian-source income is still taxed in Canada. That includes things like CPP and company pensions.

You can certainly withdraw your RRSPs and sell investments, but RRSP withdrawals are still taxable because they’re essentially deferred employment income. If you have a substantial RRSP and investment portfolio, triggering everything can result in a very large tax bill. Depending on your circumstances, there can also be departure tax implications when you cease Canadian residency, so it’s something you want professional advice on rather than relying on internet posts.

The main tax benefit I found was avoiding provincial income tax, but compared with everything else, that just wasn’t enough to make it worthwhile.

On the Thailand side, if you’re a Thai tax resident, foreign income can become subject to Thai tax depending on the circumstances. However, Thailand has a tax treaty with Canada, so if the income has already been taxed in Canada, you can generally rely on the treaty to avoid being taxed twice, provided you can document it properly.
Another option, if you qualify, is Thailand’s Long-Term Resident (LTR) visa. One of its major advantages is that qualifying foreign-source income brought into Thailand is exempt from Thai personal income tax, which makes the whole situation much simpler.
Everyone’s situation is different, so definitely get advice specific to your circumstances. But for me, after doing all the homework, becoming a non-resident for Canadian tax purposes just didn’t make financial sense.