Thai font · OFL

IBM Plex Thai

ไอบีเอ็ม เพล็กซ์ ไทย

By Narongsak Chaiwong

Typography & Licensing Specialist, ThaiGraph · April 16, 2026

Information verified as of April 2026

<link href="https://fonts.googleapis.com/css2?family=IBM+Plex+Sans+Thai:wght@400;700&display=swap" rel="stylesheet">

@import url('https://fonts.googleapis.com/css2?family=IBM+Plex+Sans+Thai:wght@400;700&display=swap');

font-family: 'IBM Plex Sans Thai', sans-serif;

What IBM Plex Thai is

IBM Plex Thai is the Thai script extension of IBM’s global Plex type system, drawn by Cadson Demak under Mike Abbink’s direction and released under the SIL Open Font License as part of IBM’s open-source corporate identity. It ships in two cuts — Plex Sans Thai (loopless) and Plex Sans Thai Looped — across seven weights with matching italics.

The original IBM Plex was designed by Mike Abbink and Bold Monday in 2017 as IBM’s new corporate typeface, replacing Helvetica after 50+ years of use. The Thai extension followed in 2018, with Cadson Demak translating Plex’s humanist-with-engineering character into Thai consonant and vowel forms.

The result is the most technically rigorous free Thai corporate sans-serif currently available. Because it carries IBM’s backing, the spacing, hinting, and opentype features are production-grade from day one.

Character design and tone

IBM Plex Thai uses sharp geometric terminals, a high x-height, and engineering-flavoured straight stems that echo the Latin Plex’s “humanist sans meeting machined hardware” brief. The loopless cut removes the traditional circle on consonants like ก and ถ in favour of clean open hooks.

What makes Plex Thai distinctive is the subtle flare at terminals — the end of a stroke on น or ม picks up a small optical widening that echoes Plex Latin’s slab-adjacent endings. Tone marks sit higher than on Sarabun, which suits the tall, architectural feel. The Looped cut is the same skeleton with traditional loops restored for legibility-critical contexts.

The Latin companion is of course IBM Plex Sans itself, which means the two scripts are drawn as one system. Cap heights, x-heights, and stem weights align precisely. A Thai sentence set next to an English sentence looks like one typeface, not two.

Weights and availability

IBM Plex Sans Thai and IBM Plex Sans Thai Looped each ship in seven weights from Thin to Bold, with matching italics. Download from Google Fonts or the IBM Plex GitHub repository.

The full Plex family also includes Plex Serif, Plex Mono and Plex Sans across multiple scripts, so a Thai + English + code-block design system can be built entirely from one family. File sizes for Plex Sans Thai are roughly 40-55KB per weight in WOFF2.

Best use cases

IBM Plex Thai is purpose-built for bilingual corporate identity, technical documentation and product UI. Strong briefs:

• Thai B2B and enterprise SaaS, particularly fintech, cloud, and dev tooling
• Technical documentation, API reference sites, engineering blogs in Thai
• Corporate annual reports and investor relations materials
• Bilingual product marketing for brands that use Plex as their global face
• Design systems for Thai government digital services that want a modern corporate feel

Where it doesn’t fit: consumer lifestyle brands (Plex reads as technical), long-form Thai editorial (the Looped cut is better, but serifs like Pridi still edge it), and traditional cultural contexts.

Pairings

IBM Plex Thai pairs obviously with the rest of the Plex family, but also with other engineered sans-serifs. Three pairings:

• IBM Plex Sans — the canonical bilingual pairing, perfectly matched by design
• IBM Plex Mono — for code samples and tabular data inside technical Thai content
• Inter — when Plex feels too branded, Inter’s humanist skeleton reads as a neutral sibling

See the typography learning hub for bilingual system guidance.

Licensing

IBM Plex Thai is released under the SIL Open Font License, which allows free commercial use, modification and bundling. This is unusual for a typeface commissioned as a corporate identity — IBM open-sourced Plex specifically so the broader community could use it. Verify the licence at github.com/IBM/plex or on the Google Fonts specimen.

Information verified as of April 2026