<Page> Exhibit 10.5(a) December 31, 2004 Mr. Peter J. Sonnabend, Vice Chairman Sonesta International Hotels Corporation 116 Huntington Avenue Boston, MA 02116 Dear Peter: We are pleased to advise you that Citizens Bank of Massachusetts has approved for your use an unsecured demand line of credit at our Prime Rate in the original available amount of $2,000,000. This line of credit will be guaranteed by certain of the Company's principal domestic subsidiaries (as described in Exhibit A). Advances under the line would be made against a revolving note, with interest payable monthly in arrears and principal payable on demand. ADVANCES WILL BE MADE ONLY IN THE BANK'S SOLE DISCRETION. To enable the Bank to monitor the Company's financial condition, you agree to submit to the Bank the following: (a) fiscal year-end consolidated and consolidating financial statements for Sonesta International Hotels Corporation audited by a CPA firm satisfactory to the Bank with 120 days after each fiscal year-end, (b) quarterly 10Q reports within 45 days after each quarter-end, and (c) such other information as the Bank may request from time to time. All expenses incurred in connection with this transaction, including but not limited to legal and appraisal fees, shall be the direct responsibility of the Borrower, whether or not this facility becomes active. This commitment shall expire thirty days from the date of this letter, unless the enclosed copy has been signed and delivered to the Bank on or before that date. 61 <Page> Mr. Peter J. Sonnabend, Vice Chairman Sonesta International Hotels Corporation January 30, 2004 Page 62 Again, we are delighted to make this accommodation available to you, and are pleased to have Sonesta as one of our customers. If you are in agreement with these terms and conditions, please indicate your acceptance by signing on the two lines designated below and returning an executed copy to my attention. Thank you. Sincerely, /S/ Lisa R. Murray Senior Vice President ACCEPTED SONESTA INTERNATIONAL HOTELS CORPORATION By: /S/ ------------------------- Peter J. Sonnabend Vice Chairman I hereby acknowledge and affirm guaranty of the above-described credit facility, by the principal domestic subsidiaries of Sonesta International Hotels Corporation as described in Exhibit A, in my capacity as authorized signer for said subsidiaries. By: /S/ ---------------------------------------- Peter J. Sonnabend, as authorized signer for Sonesta subsidiaries. 62 <Page> Mr. Peter J. Sonnabend, Vice Chairman Sonesta International Hotels Corporation January 30, 2004 Page 63 EXHIBIT A PRINCIPAL DOMESTIC SUBSIDIARIES OF SONESTA INTERNATIONAL HOTELS CORPORATION * Sonesta Hotels of Florida, Inc. Guaranty Unlimited Sonesta Coconut Grove, Inc. Guaranty Unlimited Brewster Wholesale Corporation Guaranty Unlimited Florida Sonesta Corporation Guaranty Unlimited Charterhouse of Cambridge Trust Guaranty Unlimited Sonesta Beach Resort Limited Partnership Guaranty Unlimited Royal Sonesta, Inc. Guaranty Limited to $1,000,000 * Excluding Sonesta of Massachusetts, Inc. and Sonesta Louisiana Hotel Corp. 63