Thaw squid if frozen.
Soak tamarind in a bowl with about 200 ml (approximately 7 ounces) of hot water, then stir in palm sugar until it is thick and brown and pass through a sieve. Reserve juices.
Rinse chile peppers, cut in half lengthwise, remove seeds and ribs and cut diagonally into thin strips.
Rinse scallions, trim and cut diagonally into thin rings. Set some scallion rings aside.
Heat oil in a wok, fry squid rings in portions over high heat while stirring. Add scallions, chile peppers, grated ginger and crushed garlic and fry for about 4 minutes while stirring, deglaze the wok with tamarind juice, cover, simmer over medium heat for about 15 minutes and season to taste with salt.
Serve squid on plates garnished with reserved scallions. Serve with onion rings or white rice if desired.