The original Helvetica is a commercial font owned by Monotype. Most "Helvetica Thai" versions are either:

For most users, Instead, download Noto Sans Thai or IBM Plex Sans Thai from Google Fonts—they are 100% free, legally safe, and visually very close to Helvetica.

Here are a few options for a social media post (suitable for Instagram, Facebook, or a design blog) regarding the Helvetica Thai Regular font.

Understanding technical details helps determine project compatibility. Helvetica Neue LT Thai Regular

Helvetica Thai is a modified version of the classic Helvetica typeface that includes Thai glyphs (characters). It maintains the neutral, clean, and highly legible characteristics of original Helvetica while properly rendering Thai consonants, vowels, and tonal marks.