What would a Buddhist country's law be? Does Asian countries has Buddhist law in their parliament/government?
Is there thing like this?
As we can see that Asian countries like Japan, China, Malaysia, Thailand, Mongolia, South-Korea, North-Korea, Hongkong. In these counties mostly people are Buddhist so I've to know if there is Buddhist law for parliament or government for Buddhist country. And if there what is it or what it'd be?
The guiding principles of an ideal king it to follow is the Dasavidha-rājadhamma


Dāna (charity) — being prepared to sacrifice one's own pleasure for the well-being of the public, such as giving away one's belongings or other things to support or assist others, including giving knowledge and serving public interests.

Sīla (morality) — practicing physical and mental morals, and being a good example of others.

Pariccāga (altruism), being generous and avoiding selfishness, practicing altruism.

Ājjava (honesty) — being honest and sincere towards others, performing one's duties with loyalty and sincerity to others.

Maddava (gentleness) — having gentle temperament, avoiding arrogance and never defaming others.

Tapa (self controlling) — destroying passion and performing duties without indolence.

Akkodha (non-anger) — being free from hatred and remaining calm in the midst of confusion.

Avihimsa (non-violence) — exercising non-violence, not being vengeful.

Khanti (forbearance) — practicing patience, and trembling to serve public interests.

Avirodhana (uprightness) — respecting opinions of other persons, avoiding prejudice and promoting public peace and order.



King Asoka incorporated this into his rule and perhaps some other monarchs historically.
Sri Lankan constitution does gives the following provision.

The Republic of Sri Lanka shall give to Buddhism the
foremost place and accordingly it shall be the duty of the State
to protect and foster the Buddha Sasana, while assuring to all
religions the rights granted by Articles 10 and 14(1)(e).

THE CONSTITUTION OF THE DEMOCRATIC SOCIALIST REPUBLIC OF SRI LANKA (As amended up to 15th May 2015) Revised Edition – 2015
Thai Monarchy seem to have it engrained:

Thai concepts of monarchy have their origins in Sukhothai, founded in the early part of the 13th century and generally regarded as the first truly independent Thai kingdom. Here, particularly under the reign of King Ramkhamhaeng the Great (1275-1317), was born the ideal of a paternalistic ruler alert to the needs of his people and aware of the fact that his duty was to guide them. Such forms part of Dasavidha-rājadhamma, or the ten precepts of kingship, which – rooted in the tradition of Theravada Buddhism – encompasses such virtues as willingness to give and sacrifice for a greater good, morality, honesty, open-mindedness, diligence, compassion, perseverance and righteousness.

Thai Monarchy
But not sure the Dasavidha-rājadhamma is directly found in the constitution or any legislature any of the modern day Buddhist countries. At least it is not the case in Sri Lanka. Mainly because the constitution and legislature is modeled what was inherited from the British rule and constitutions and legislation of other countries.