The song is in D.
Although chords change, the bass note remains D throughout.
(D)Nila kaaygiradhu naeram thaeygiradhu yaarum rasikkavillaiyae
Indha (G)kangal mattum unnaik (A)kaanum
(D)Thenral poaginradhu soalai sirikkinradhu yaarum sugikkavillaiyae
Indha (G)kaigal mattum unnaith (A)theendum
(D)Kaatru veesum veyyil (A)kaayum kaayum adhil (G)maatram aedhum illaiyae
Aaaaaa...(D)Vaanum mannum nammai (A)vaazhach chollum andha (G)vaazhththu oayavillai
(D)Adho poaginradhu (A)kaanal maegam (D)mazhaiyai (G)kaanavillai(D)ye
(D)Idho kaetkinradhu (A)kuyilin sogam (D)isaiyum (G)kaetkavillai(D)ye
Indha (D)bhoomiyae (A)poovanam endhan (G)poovidhazh (D)saruguthae
Indha (D)vaazhkaiyae (A)seedhanam adhil (G)jeevanae pova(A)then
Stop existing and start living!