You write "Hey, how's your evening going? Miss you x". Here is what happens next, and why it matters for what you write.
On a messenger that translates in the middle, she gets a Thai sentence on the LINE she already uses. No bot, no copying. The tone survives if the message was simple. "How is your evening" comes through cleanly. "Miss you x" comes through as "miss you" and the kiss is dropped, because Thai has no letter that does that job.
Warmth, plans, photos, and questions with one answer. "I land on the fourteenth. Are you working that week?" is a perfect message: two short sentences, a date, a question she can answer with one word.
Her Thai comes back to you as English, with her original underneath. The English will sometimes be blunt, because Thai drops pronouns and softeners. "Tired, work" is not a brush-off. It is a woman telling you about her day in the fewest possible words, which is how Thai is written.
Write short, write plain, and write about something. She will read all of it.