Thank you for your answer.
However, I assume that being on LTR means I can't apply for Thai citizenship. Right?
If the above is right, I have a dilemma i.e. I can stay on non-immigrant O marriage visa, pay taxes and have the WP for 3 consecutive years and then apply for Thai citizenship or go for LTR and to not pay for taxes but not being eligible to apply for Thai citizenship. Did I get it right?