I don't know if there is a law, but I have only seen one person use a car seat in Thailand. In the back seats, no one even wears seat belts.
A sling/backpack carrier would probably serve you better than stroller. Uneven, cluttered, crowded sidewalks aren't conducive to carriages.
Stick to busy, hot-off-the-burner delights, and you will be fine. The finest food in Thailand is from the small carts, stalls, and shops. With limited menus, they do a better job.
Most contamination comes from your own hands. Bring along plenty of sanitary wipes and tissues for cleaning up before eating.
Many small eateries use a single wok. If they serve any pork dishes, the pork has hit the wok. Although they rinse and scorch the woks, there may still be some pork "seasoning".
I strongly recommend Hep A vaccination for anyone, anywhere. Personal hygiene is practiced so rarely, worldwide. A friend was concern about the cost of the vaccine, so he asked a Los Angeles clinic operator if Hep A vaccine was really need for Thailand. He was told that Hep A was needed for Los Angeles !!!
I would consult a doctor about Hep A vaccine with a young child.
Thais aren't typically "outgoing". It would be difficult to form a personal relationship in such a short time. There are homestays, but I don't know how real these may be.
You can, however, let your kid run loose at a McDonalds, KFC, or a Central Department Store's play area. This might also be a foot in the door for a lunch invite.
Unless you are heavily pounding the boarder regions, Malaria isn't really a concern. Dengue is another matter.
We have had limited success with lemon grass based repellents, but they need constant re-application. We have returned to a mild deet lotion.
Around larger cities, great medical care can be found. As an herbalist, you are doing a lot of your own doctoring anyway. If you require any heavy medications, Thai pharmacies will dispense just about any medication, unless they possess any "recreational" value. Antibiotics, antihistamines, and such are dispensed OTC.
It's might not be a bad idea to get emergency evacuation medical insurance, just in case of something catastrophic occurs. Maybe mom will spring for it.
If you are in Bangkok, during a weekday lunch period, I would strongly recommend United Center Silom's 3rd floor food court. Here you will find my ->favorite vegetarian eatery<-
in the world (this, from a hard core meat eater!).
United Center is next to Bangkok Bank, across Silom from Bangkok Christian Hospital.
Here are some ->additional suggestions<-
. The carts are small, single item eateries, the woks are food courts, and the fork/spoons are more sit down restaurants