Is There a Single Common Language in Asia?

No. Asia is the most linguistically diverse continent, home to ~2,300 languages (nearly 1/3 of the world's total) across 10+ language families:

Major Families & Examples

• Sino-Tibetan: Mandarin (1.1B), Cantonese, Burmese, Tibetan, Karen.
• Indo-European → Indo-Iranian: Hindi/Urdu (600M+), Bengali (270M), Punjabi, Persian, Pashto, Nepali.
• Austronesian: Javanese, Malay/Indonesian, Tagalog, Malayalam (wait—Dravidian), Sundanese, Maori (Pacific).
• Dravidian: Tamil, Telugu, Kannada, Malayalam (South India, Sri Lanka).
• Altaic (controversial): Turkic (Turkish, Uzbek, Kazakh), Mongolic, Tungusic.
• Afro-Asiatic → Semitic: Arabic (Levant, Mesopotamia, Arabia).
• Tai-Kadai: Thai, Lao, Zhuang.
• Austroasiatic: Vietnamese, Khmer, Mon, Santali.
• Japonic: Japanese, Ryukyuan.
• Koreanic: Korean, Jeju.
• Isolates: Ainu, Nivkh, Burushaski, Kusunda.

Lingua Francas (Regional, Not Continental)

• English: Business, science, tech, diplomacy (India, Philippines, Singapore, HK, Gulf).
• Mandarin: China, Taiwan, Singapore, diaspora.
• Russian: Central Asia, Caucasus, Mongolia (legacy).
• Arabic: Middle East, liturgical.
• Malay/Indonesian: Maritime SE Asia.
• Hindi/Urdu: South Asia.

Asia's linguistic map is a mosaic, not a monolith.