How to prepare a picky eater for Thai, Cambodian, and Vietnamese cuisine?

Most typical Thai food is very flavorful. There is certainly a fare share of spicy dishes but there are also plenty of other flavors, herbal, fragrant, salty and sweet. Obviously, the difficult part is knowing which is which!

Many of the dishes are not so spicy or salty themselves. Instead, restaurant tables come with small bowls of Nam Pla with chopped chilies floating in them. People scoop this and mix it into the food on their plate after they have taken a portion from a shared serving plate. This makes it possible to make the meal more salty and spicy at the same time. It is difficult to make it more spicy without getting too salty which is the problem I had since I like food very hot but not so salty.

The nice thing is that a group can try different dishes since many dishes are meant to be shared. They can order a few, try them and learn which ones they like. Some curries are relatively mild such as the yellow curry which usually includes potatoes (this is completely different from Indian curry of the same color). Green curries are almost always hot and so are red curries.

The milder dishes are usually grilled marinated meats, either skewered or served over rice. Many rice and noodle dishes are also mild in flavor since they are meant to balance strong flavors from curries and herbs.

When all else fail, order spaghetti or pizza. Almost every Thai restaurant anywhere near tourist areas has one or both of these items specifically for picky foreigners. Since my favorite food is Thai, I have not tried these personally but I wouldn't expect either to be fantastic. You actually often see couples in restaurant with one of the two being Thai and eating Thai food and the other with a plate of spaghetti.

In Vietnam food is completely different. Most of it is much milder in flavor with light seasoning. Grilled meats again are quite popular and can also come with rice or noodles, mostly quite plain, or served in a elongated bread as a sandwich. No idea about Cambodia.

Vietnamese Pho (most variants anyway- iirc Hue type is already spicy) noodle soup have the spice optionally added by the end user. Similarly the rice and vermicelli dishes are not inherently spicy (the fish sauce may not be to their liking but again that's typically on the side). The little baguettes (banh mi) are typically a bit spicy and include stuff like head cheese but are pretty delicious. You can get plenty of rather good Viet food in Canada, so worth getting started early. Don't miss the coffees.

For Thai food there is always pad Thai (noodles). Again, domestically available. And there are enough foreigners they can probably get something that looks even more familiar.

I don't recall Cambodian cuisine that well, but I don't think it is particularly spicy or weird tasting. I recall their pizza being quite good. I'm unsure of the legality but one of the available toppings may be cannabis, aka 'happy pizza'.

Anyway, as I discovered with my young (at the time) son, hunger is a powerful motivator.

Thailand-specific advice here from someone who doesn’t tolerate any spice at all.

In my experience, in Thailand there’s a huge number of small low-key local shops serving basic meals like rice/noodles + chicken/beef 100% bland by default, with spices available on tables.

My go-to option in an unfamiliar location would be a chicken rice. It’d generally be a small local shop, not very fancy looking, with one chicken rice dish costing about 30–40 baht, usually served with a little bowl of soup.

Tip: In my experience such shops operate from around 10am to 3pm. It might be worth going there early after opening, they appear to keep cooked rice around for hours in warm weather which can be unhealthy and/or unsettling.

Pad thai I got spicy a few times so I’m not going with that one generally unless I’m with a partner who can eat it in case it turns out to be spicy.

For the reference “chicken rice” in Thai is written as ??????????, where ??? is chicken (remembering how it looks could prove helpful), and ???? is rice. Sellers might just recognize if you say it in English though.

While I've never been in Cambodia or Laos my experience with various other countries around there is that fried rice is almost always a safe dish heat-wise and it's obviously not too adventuresome. I ate a lot of it in that part of the world as something I knew wouldn't burn me.

I worked in Cambodia for a year. One of my favorite dishes was lok lak. It's basically seared beef cubes, sometimes sliced, sometimes in sauce. It's usually served with a little dish of lime juice and ground black pepper on the side for dipping.

As Loren stated, fried rice is usually a safe bet, as are fried noodles (mee chah).

Sweet & sour pork is fairly common there, but sweet & sour chicken is not. Some of the best sweet & sour pork I've ever had was at a little hole-in-the-wall place in Phnom Penh.

Pho is a very common dish in all three countries--but I can't recall the Cambodian or Thai names. In Cambodia, it's usually eaten for breakfast. I don't recall ever eating it at another time of day.

Frog legs are not uncommon in Cambodia. I always just ate them grilled/roasted. Not spicy at all. Very much like popcorn chicken stuck with toothpicks.

It sounds like your parents will likely be going to places that are used to serving tourists. Those places usually have menus in English and frequently include pictures and spice guides. And Cambodian cuisine tends to be more sour than spicy.