Mortuary Service Administration Act Article 27

When burying coffins, the surface of the coffin shall be at least seventy centimeters deep below the ground level, the top of the grave shall not exceed one meter and fifty centimeters above the ground level, and the grave shall be tightly sealed. However, those with local customs or special geological conditions who have reported to the special municipality or county (city) competent authority and gained approval may not be subject to this restriction. The maximum height of the tomb stone shall not exceed two meters above the ground.Ash burials shall be done in planar. Since those can be done due to public art modeling designs with the approval from the special municipality or county (city) competent authorities, they are not subject to this restriction.
中文原文 殯葬管理條例第27條
埋葬棺柩時,其棺面應深入地面以下至少七十公分,墓頂最高不得超過地面一公尺五十公分,墓穴並應嚴密封固。
但因地方風俗或地質條件特殊報經直轄市、縣(市)主管機關核准者,不在此限。
其墓頂最高不得超過地面二公尺。
埋藏骨灰者,應以平面式為之。
但以公共藝術之造型設計,經直轄市、縣(市)主管機關核准者,不在此限。

English translation for reference only; the Chinese text prevails. Not legal advice.