The parade, part of the Bangkok Naruemit Pride 2022 event, will start at the Indian temple (Wat Kaek or Sri Mariamman) at 4pm and run until 7pm.
The afterparty will be held at Mischa Cheap in the Khaosan area from 9pm. Revenue from the 400-baht party entry fee will be used to promote future gender equality events, including Songkhla Pride on June 26.
Jirajet Wisetdonwai, a member of Bangkok Naruemit Pride 2022, said the parade will see LGBTQIA+ people and their supporters call for equal marriage, safe abortions and an end to sexual violence.
LGBTQIA+ groups have been organising small Silom parades since 2013, he added.
Jirajet pointed out that calls for legal change by citizens, organisations and political parties, Thai law does not support gender diversity.
LGBT Pride month is being celebrated around the globe to commemorate the landmark Stonewall uprising, when the gay community of New York rose up against police oppression in June 1969.
Former US president Bill Clinton enshrined June as "Gay & Lesbian Pride Month" in 1999 while his successor Barack Obama declared June as LGBT Pride Month in 2009.
The abbreviation LGBT was coined in the 1980s by gay rights activists. Over the past 40 years, it has expanded to incorporate more sexual orientations, and LGBTQIA+ is now recognised across the globe.