How to use PromKhai

The home page shows your shop name and today's date, split into two tabs:

• Overview — a "Sell now" button that opens the checkout screen; stat cards for today's sales, bills, and profit; a shift-status card (with an "Open shift" button if no shift is open yet); alerts for low-stock products (tap through to the Products page) and overdue customer credit; a shortcut row to Products, Customers, Sales, and Settings; and a recent sales list with a "View all" link
• Sales Report — a chart summarizing sales over time, for an overview of how the shop is performing

• Tap "Add product" to create a new product — name, price, unit (piece/kg/liter/pack), cost price, starting stock quantity, category, barcode, and SKU
• Use the search bar or barcode scanner to find existing products, and filter by category
• Tap a product to edit it, or tap the stock-adjustment icon to restock or reduce stock
• The gear icon at the top lets you set the "low stock" threshold, the VAT rate, and manage product categories
• You can delete a product from its edit screen; if it already has sales history, it's archived instead of deleted outright

• Before selling, you must always open a shift first by entering the starting cash amount in the drawer — the shift status bar shows at the top of the sell screen
• Search for products by name/SKU/barcode, or tap "Use scanner" for continuous barcode scanning — items get added to a running cart
• Adjust item quantities with the +/− buttons, or remove an item from the cart
• Tap "Pay" to open the payment screen — enter a discount, toggle VAT, and choose a payment method (Cash / Transfer / PromptPay / Card / Credit)
• Selecting "Credit" requires choosing a customer from the list first
• For cash payments, an "Exact amount" shortcut is available and change due is calculated automatically
• Tap "Confirm sale" to finalize the bill, then share, print (via a Bluetooth printer), or download the receipt as a PDF
• Remember to "Close shift" at the end of the day to reconcile the cash drawer

• View every past sale, with its total, date/time, and payment method
• Tap a sale to see its line items, and reprint, re-share, or re-download the receipt
• You can "Void" a sale if it was entered by mistake — a reason is required

• Tap "Add customer" and enter a name (required) and phone number
• Customers with an outstanding balance show a credit chip in the list
• Tap a customer to "Record payment" when they pay down their balance (amount and an optional note)

• Account — see the signed-in name/email, and "Sign out"
• Subscription — renew, subscribe, or restore a previous purchase
• Language / Theme — change the app language, and switch between system/light/dark theme
• Data sync — see the last sync status and tap "Sync now" to sync immediately instead of waiting for the automatic interval
• Bluetooth printer — select, change, or clear a receipt printer, and run a test print
• Delete account — erases all shop data on this device and signs you out (requires confirmation — this cannot be undone)

If you use the app on multiple devices signed in with the same Google account, your products, sales, and customer data sync between them automatically via Google Drive — every 10 minutes while the app is open and online, and immediately whenever the app launches.

• The sync indicator in the bottom-right corner spins while a sync is in progress
• If a sync fails, a red icon appears with a message explaining why
• The app keeps working normally without an internet connection — it syncs as soon as it's back online

Note: if two devices edit the same data while both are offline, whichever syncs later may overwrite the other's change. Sync often (or tap "Sync now" in Settings) whenever you have an internet connection.