Sibling dynamics are always morphing: peas in pods one minute, chalk and cheese the next. Sibling Spice rings the changes too. This shifting feast is a cruisy cafe by day and a full throttle Thai restaurant by night, so busy that I saw waiters literally run between tables to take orders.

The restaurant is owned by the Sorataworn family, who have been part of the Koornang Road fabric for 14 years, first with popular Paradai Thai (across the road) and then with Paradai 2 (next door).

Now son James and his wife Bee are part of a new wave ushering Carnegie's transformation from a tasty suburban strip into the Flinders Lane of the south. They haven't finished yet: the original Paradai will soon reopen as a trendy Thai soup noodle joint. Fishball fans, get ready.

In the meantime, Sibling Spice undoes all the suburban Thai restaurant cliches. The 100-seat restaurant looks like a high school gym with mesh fencing, vinyl flooring and blackboard-green detailing. There are no elephant decorations, silk throws or lanterns to be seen. It's bright, energetic and enormously popular, especially for dinner.

Come in the morning for good coffee (or matcha latte) and a fusion menu that includes chicken-and-prawn dumplings with chilli vinegar, avocado mango salad on toast, bubble waffles with raspberry sprinkles, and an excellent breakfast ramen, served on a canteen-style tray with a rich bacon broth to pour over the noodles yourself.

Thai favourites like green curry and stir fries are served at lunch (along with burgers and tacos) but it's after 2.30pm when the kitchen team swaps over and the Thai menu really beefs up.

Speaking of beef, my favourite dish is the massaman curry of slow-cooked beef with potatoes and cashews. The spicing is mild with the tartness of tamarind and pineapple spearing their way through the creamy coconut base.

Wokked noodle dishes are satisfying too; the pad khee mao is a sticky tangle of fat rice noodles with vegetables and Thai basil.

Green papaya salad is always a good test of a Thai restaurant and Sibling Spice's som tam comes through. Chilli, garlic, tamarind and palm sugar are pounded to a paste and tossed with shredded unripe papaya. Thai street vendors often serve the classic salad with preserved salted crab; here you can have it topped with fried soft-shell crab in a deluxe Melbourne spin.

The food is serviceable to good; flavours are honest but not always punchy and the happy problem of popularity can mean dishes look a little slapdash. You can BYO wine and perhaps you should because half the bottles on the tiny list were unavailable when I visited. It can also be challenging to halt a sprinting waiter to put in an order.

On the up-side, there is banana roti for dessert, the kind of simple indulgence that smooths over all glitches. A common Thai street snack, banana is cooked up in fried roti dough, then drizzled with sweetened condensed milk. Caramelised banana and buttery dough: there's nothing not to like.

Carnegie is on the up with new skyrails, hundreds of apartments and a bunch of hospitality operators springing up to feed the shiny new hood. Sibling Spice is part of a vanguard, an all-day neighbourhood dining room that takes 3163 from coffee all the way to bedtime.

Rating: Three and a half stars (out of five)