The Thai version of the "protocol between Japan and Thailand concerning the guarantee and political understanding" dated 9 May 1941 <a href="https://en.wikipedia.org/wiki/Common_Era" class="extiw" title="w:Common Era">CE</a>, and the royal proclamation of King Rama VIII of Thailand dated 5 July 1941 <a href="https://en.wikipedia.org/wiki/Common_Era" class="extiw" title="w:Common Era">CE</a> promulgating it, as published in the Thai Government Gazette on 5 July 1941 <a href="https://en.wikipedia.org/wiki/Common_Era" class="extiw" title="w:Common Era">CE</a>.
Government of Thailand
1941-07-05
<a rel="nofollow" class="external text" href="http://www.ratchakitcha.soc.go.th/DATA/PDF/2484/A/889.PDF">Royal Thai Government Gazette, volume 58, issue 0 A, dated 5 July 1941, pp. 889–893</a>