[stfatt]

Mine wife is also from Thai. I also got married in Thai using Thai marriage cert. Now she also holding LTVP and renew in 5 years time as she is on 2nd renewal.
1) you can use your Thai marriage cert translated to English for apply in LTVP.
2) Actually I have asked before whether need marry in Singapore again but ROM say no need as mine marriage cert is official recognized in legal although I got married in Thai.
3) income wise that time I was holding 2.2k.
4) if you have kids will be more easier as at that time I have kids when applying LTVP.