Interface language, said plainly
HelloGrowthCRM is English-first. In a team where sales staff work primarily in Thai, that is a real consideration and not a footnote. Thai text in names, notes and messages is stored and searched normally, but the menus and settings are English. Put your least English-comfortable rep in the pilot and judge adoption on their behaviour.
Billing currency
The subscription is charged in US dollars while your revenue arrives in baht, so agree who holds the card, whether monthly billing is available during evaluation, and what an annual commitment locks in. A genuine free tier lets you postpone that decision until the pipeline is running and the value is obvious.
Invoicing and payment
Keep tax invoicing where it belongs, in the accounting system that issues your VAT documents in Thai and files them with the Revenue Department, and use the CRM for the quote, the approval and the chase. Payment usually arrives by bank transfer or PromptPay, often against agreed terms, so record the promised method and date on the deal to make the collection call concrete.