ABSTRACT
Background An earlier study by Punsongserm and Suvakunta (2022) investigated how using proper typefaces and type sizes on Thai drug packages and patient information leaflets affects reading times and participants' satisfaction. The study was an initial review of the use of Thai typefaces focusing on typeface classifications and type sizes. The study also conducted a pilot study with participants who read small sample text cards that varied by typeface and type size. To extend the results of the previous study, this current study is a set. Methods First, we conducted a literature review about guidelines and regulations governing typefaces and type sizes on drug labeling and drug documentation, followed by an investigation of word accuracy identification in reading Thai transliterated words on drug documentation. Later, we measured user preference in different typefaces and type sizes through user manuals of the SARSCoV-2 Antigen Test Kit (ATK) with and without wearing cataract-experiencing goggles. Results The conventional text typefaces with distinctive key letter features have a lower misreading in word accuracy. Also, the most satisfaction in the user preference test importantly indicate a user manual that provides a conventional text font with a larger type size. The international guidelines recommend a minimum type size of 6 points or 1.4 mm of x-height. In contrast, Thailand's national regulation suggests a minimum size between a Bo Baimai height of 1–2 mm for food labels and more than 2 mm for drug products. However, we recommend that a Thai type size may be 1.3–2 mm of Bo Baimai height for reading body text, and the type size for headlines and subheads should be more remarkable. The use of smaller type sizes needs a case-bycase evaluation basis based on legibility and readability. Conclusions The present study examines how using proper typefaces and type sizes on Thai drug packages, patient information leaflets, and medical products affects reading accuracy and participants' satisfaction. The study suggests that using illegible typeface and very small type size on many Thai drug packages, patient information leaflets, and medical products may be inappropriate and not serve a variety of readers. Therefore, the review and enforcement of the law should be considered in conjunction with developing guidelines and regulations based on user-centered care. © This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons. org/licenses/bync/3.0/), which permits unrestricted educational and noncommercial use, provided the original work is properly cited.