correct doha however will be written as जब मैं था तब हरि नाहिं, अब हरि है मैं नाहिं | सब अंधियारा मिट गया, जब दीपक देख्या माहिं || here i have written नाहिं/माहिं because these satisfies essential rhyming in a doha, नहीं is also sounding fine but i never knew whether महीं existed, anyway7 u can doubt it. i really appriciate ur very accurate knowlege of hindi but this doha isnt written in modern standard hindi, so those stringent kind of rules doesnt apply नहीं is 100% correct usage in modern standard hindi, नही is 101% wrong, anuswaar is essentail, i would humbly like to ask to to give references if "nahi" (not naheen) is ever used in hindi literature. dekhya isnt standard hindi but in north western languages or dialects and in khadi boli we see its usage, maarwari dialect is one example. you are very correct in ur knowledge but this time it is a different picture, perhhaps khadi boli, i m afraid i cant help u out more here, because to do it i have to consult real pundits my parents :D some may tell u it with great and better insight but what i understood, after contemplating a little is jab main tha tab mujhe main hi main dikhai deta tha (ego), i was never able to see god(hari) , but ab jab main hari ko jaan chuka hoon, i understand that i m nothing, main kuchh hoon hi nahi, maahin means within (those who doubt me can clarify from this doha itself ज्योतिल माहिं तेल है चकमक माहिं आग | तेरा साईं तोय में जाग सके तो जाग ||) just try to figure out it in ur own way जब मैं था तब हरि नाहिं(when it was i, there was no 'hari'), अब हरि है मैं नाहिं(now ther is 'hari', not me) | सब अंधियारा मिट गया, जब दीपक देख्या माहिं ||(in last line i think he says that darkness of "agyaan" vanished probaly by self illumination) i tried my best i hope for a better answer, either someone gives or u figure it out, as kabir das says so :) :)

hello you asked 3 questions here. 1.about नही\ , what you said is right, but india is very big country, hindi is spoken in many different ways. in some states people use नही in place of नहीं. some times poet uses नही to creat a certain form of poem. [for this, you have to know about some certain rules those are used in indian literature for writing poem so that poem can be nice and attractive.] 2. for देख्या\ देखा . the answer is same as above. 3. माही/माहीं is name of some one which means 'the earth'. in indian literature some times poet chooses to write a poem addressing some one. so here the poet addresses a person named mahi.