Fourth reign

Mongkut (Rama IV) felt the need to create a Royal standard to distinguish his royal barge from other vessels during his many travels around the Kingdom and to fly above the Grand Palace when he is in residence. In 1855 a Royal Standard was created called the 'Thong Chom Klao' (ธงจอมเกล้า).

The standard featured a red rectangular flag with a smaller dark blue rectangle inside. Within the dark blue rectangle depicts the Great Crown of Victory on a stand flanked by two seven-tiered Royal Umbrellas. The Crown itself is derived from the King's personal seal, which in itself is a canting of both his given name and ceremonial name: Mongkut (มงกุฎ) and Chom Klao (จอมเกล้า) both meaning 'Crown' in Thai. The crown and the umbrellas are situated on a golden platform.

However the sight of an empty flagpole when the King was not in residence at the palace was considered inauspicious, therefore a second flag was ordered to be hoisted during the King's absence. This flag is called the 'Thong Airapot' (ธงไอยราพต), the rectangular red flag depicts a mythical three-headed white elephant (Airavata) in full regalia standing on a golden base with a golden pavilion on its back. Within the pavilion is the Thai symbol for Aum or Unalom. The elephant is then flanked on two sides are two seven-tiered Royal Umbrellas.

Fifth reign

In 1891, King Chulalongkorn (Rama V) decided to promulgate a new law to reform the Royal Standard and create for the first time ranks flags for members of the Royal Family. The Royal Standard was changed by adding the new Arms of Dominion, which is a golden shield divided into three parts. The first in yellow depicts a three-headed mythical elephant representing Siam, the second quarter in red depicts a single white elephant for Laos (Lan Xang) and the third quarter in pink depicts two crossed Krisses for the Malay suzerainty (Siam was later forced to relinquish these territories by the French and British, respectively). Inside the crown the symbol for the Chakri Dynasty is added; it depicts an intertwined Chakra and Trisula. The flag ratio is 5:6 The name of the Royal Standard was then changed to 'Thong Boromrajathawat Maha Siaminthra' (ธงบรมราชธวัชมหาสยามินทร์), A few years later in 1897 the name was permanently changed to 'Thong Maharaj'.

The King retained the second colours by replacing the Unalom with his own Royal cypher (จ ป ร, derive from "จุฬาลงกรณ์ ปรมราชาธิราช": Chulalongkorn Paramarajadhiraja; equivalent to Chulalongkorn Rex), which in turn is topped by the Royal Coronet or Phra Kiao (พระเกี้ยว). The name of this flag was also changed to the 'Thong Chudhathipathai' (ธงจุฑาธิปไตย).

Sixth reign

In 1910 Vajiravudh replaced the Royal Standard and Royal rank flags to mirror the change of the national emblem from the Coat of Arms of Siam to the Royal Garuda. These flags are retained and in use to this day. Six years later he also redesigned the national flag and naval ensigns.