Child medicals beware
It must be taken in to consideration that if you apply for an Australia spouse or fiancee visa for your Thai partner that even though they have a medical also their Thai children must be checked also and this is where we are now constantly seeing problems.
Unfortunately in some cases were children are involved traveling or not they could have a medical problem that could stop your Thai spouse from getting their spousal visa to Australia. The Australian Embassy can be very harsh with migration visa applications even if the children of your partner will never be traveling to Australia.
If your Thai partners Child or children are found to not have passed the Government medical then a health waiver system comes in to play were the Australian Government want to see all financial details of how you could take care of the child in Australia if the child was to travel, you saying the child will never travel is not enough for the Australian Embassy As circumstances could change including the guardians of the child/children in Thailand could fall sick in the future and the child has to travel to be with the mother.
So even though it is difficult to ascertain if the child has any medical problems, if you are aware then take this into consideration before applying as it could cause you major problems in the future.