First of all, since you were in Thailand,
and since it all started with vomiting
and diarrhea, it is important to get a stool test to rule out parasitic infestations, especially amoebiasis, giardiasis, tape worm, round worm, etc. All these can cause malabsorption, anemia, weight loss etc. The anemia and weakness can cause the heart to beat faster. So, along with stool test you need to test for anemia, low vitamin B12, and electrolyte imbalance.