Short answers, pulled from the story.
The iconography of Gautama Buddha in Laos and Thailand is a formal system of rules governing how the Buddha may be depicted, covering posture, dress, and hand gestures called mudras. Each combination of posture and mudra corresponds to a specific episode from the Buddha's life. The canon was not fully formalised until the 19th century.
A mudra is a hand gesture used in Buddha images that carries a defined symbolic meaning. Six core mudras are associated with the Buddha in Laos and Thailand, ranging from the Bhumiparsha mudra (calling the earth to witness) to the Dharmachakra mudra (setting the wheel of teaching in motion). Combined with body posture, they identify specific moments in the Buddha's life.
Paramanuchit Chinorot, a son of King Rama I and administrator of Wat Pho in Bangkok from 1814, formalised the canon at the request of King Rama III. He produced an illustrated treatise called Pathama Sambodhikatha describing 40 distinct postures of the Buddha. His illustrations were later cast as bronze miniatures, now held at Wat Phra Kaew in Bangkok.
The ushnisha is a protuberance on the top of the Buddha's skull, listed among the 32 physical attributes described in the Digha Nikaya, a Pali text of the 1st century BCE. It appears in different forms depending on the tradition, including as a spire, a spike, or a small rounded bump.
The long earlobes on Buddha images recall the heavy jewellery worn during Gautama's earlier life as a prince, which stretched the ears over time. The feature has since come to symbolise wisdom in Buddhist iconography.
The Bhumiparsha mudra is by far the most commonly depicted in Thai and Lao temples. It shows the right hand resting on the right thigh with fingers pointing downward toward the earth, while the left hand lies palm-up in the lap. In Thai it is known as the Buddha subduing Mara, the demon who tried to prevent his enlightenment.