Due to our colonial past, quite a number of Dutch people are from Indonesian origin. In Amsterdam one can find dozens of Indonesian restaurants and take-aways. Vegans will find plenty options. Since little dairy is being used in the Indonesian cuisine, many of the vegetarian dishes are automatically vegan. One of the staples of vegan Indonesian food is tempeh, the versatile protein source made from fermented soy beans. You have to try it!
Betawi is a nice little Indonesian restaurant and take-out in the west of Amsterdam. Their menu specifically lists all vegetarian options, including dishes with soy meat. They also serve Thai food. Usually so called vegetarian dishes in Thai restaurants are not actually vegetarian due to the use of fish sauce. But at Betawi they can use a vegan replacement, great!
If you call in advance and let them know you’re vegan they can cater for you optimally, although it’s not required.