It has been common knowledge for the past two years that if you required a partner/marriage/ prospective marriage visa for your Thai partner and the Thai National had children from a previous relationship they would have to under go full medicals the same as the applicant even if the children were not traveling.
This has always been an absurd rule as it has not always been easy for the Thai applicant to gain access to their Thai children due to ex partners or family issues which has caused them unforeseen problems with the visa application or even lead to a reason for refusal.
Also if the Thai child from a previous relationship had a sickness that the Australian Embassy/ Government deemed would lead them to a burden to the state then they could also refuse the visa.
This has now changed and the children if not traveling are not an issue and also not required to go for a body medical it is only children who are traveling need a body medical so make sure that you are aware the child is fit and well before applying for a spousal/ prospective marriage visa to Australia.
For more info e-mail Darren at [email protected]