FAIK. A two wheeler of 50cc is allowed without a separate license
Edit things may have changed
For reference: They have changed the law - it depends on the issue date of the license now:
https://www.thb.gov.tw/News_Toggle.aspx?n=11532&sms=13070
汽車駕駛執照可否騎乘機車？
1.依據道路交通安全規則第61條第1項第4款規定：「已領有小型車駕駛執照者，得駕駛輕型機車」，另依同條第2項規定，中華民國一百十二年六月三十日起新考領之汽車駕駛執照不得駕駛輕型機車。
2.另依同條第5項規定：「機車駕駛執照於吊扣期間或經吊銷後，不得持汽車駕駛執照駕駛輕型機車」。
3.依道路交通管理處罰條例第22條第1項第5款規定：「領有聯結車、大客車、大貨車或小型車駕駛執照，駕駛輕型機車者，處新臺幣一千八百元以上三千六百元以下罰鍰，並禁止其駕駛。但中華民國一百十二年四月十四日修正之條文施行前已取得該汽車駕駛執照者，不在此限
Can a car driver’s license be used to ride a motorcycle?
- According to Article 61, Paragraph 1, Subparagraph 4 of the Road Traffic Safety Regulations: “A person who holds a small vehicle driver’s license may drive a light motorcycle.” Furthermore, pursuant to Paragraph 2 of the same article, car driver’s licenses newly issued on or after June 30, 2023, may not be used to drive light motorcycles.
- Furthermore, pursuant to Paragraph 5 of the same article: “During the suspension period or after the revocation of a motorcycle driver’s license, a person may not drive a light motorcycle using a car driver’s license.”
- Pursuant to Article 22, Paragraph 1, Subparagraph 5 of the Road Traffic Management and Punishment Ordinance: “Any person holding a driver’s license for a tractor-trailer, large passenger vehicle, large truck, or passenger car who operates a light motorcycle shall be subject to a fine of not less than NT$1,800 and not more than NT$3,600 and shall be prohibited from driving.” However, this provision does not apply to individuals who obtained such a motor vehicle driver’s license prior to the implementation of the amended provisions on April 14, 2023.”