you currently have 145/80 R12.
I would suggest you go for 13inchers, 155/65 or 155/60 would be the best choice for you.
And if you want comfort tires go for Michelins,
Or if you want all-round tires, little comfort + plus long life, then i suggest Yokohama A-Drives.
Best of luck, and do post a picture, when you get them :)
I have Yoko A-Drives 13" on my Alto from previous two years and i have clocked 33k with these, they are smooth as butter, a lot of tread is still visible on them