Don Quijote has a global online store at mpglobal.donki.com  and it does ship to Singapore directly via EMS.
Prices on the site are much cheaper than getting from Don Don Donki in Singapore.
Shipping charges are reasonable too. Singapore belongs to Region 2 alongside Thailand, Indonesia, Malaysia, and India. For Region 2, shipping a 1 kg parcel via EMS will cost JP¥1,050 (S$14).
In contrast, Ichiran is retailing for S$39.90 at Don Don Donki which is now out of stock and UHA Mikakuto Croquette Snack at S$2.90.
I have not tried buying from Don Quijote Online Store yet. But I will try it once my Ichiran stock is low.
Tried checking out to get an estimate of prices, two Ichiran plus shipping will cost you: JP¥1,980 + JP¥1,980 + JP¥1,900 = JP¥5,860 (S$73). That works out to be about S$37 per box which is slightly cheaper than Don Don Donki.
Of course for online shopping, the best is to consolidate all your orders to split the shipping costs, and it will be cheaper than getting from Don Don Donki.